Internal combustion engines for vehicles include those wherein cylinders are disposed in series or in opposed relationship, bank cylinders are arranged in the form of a V, i.e., a V-type internal combustion engine, and so on. The V-type internal combustion engine includes first and second cylinder banks in a V-shaped cylinder block on which first and second cylinder heads are mounted. These cylinder heads are covered with first and second cylinder head covers.
A crank shaft extended lengthwise of the internal combustion engine is arranged rotatably bidirectionally at a generally central portion of the cylinder block mentioned above. The crank shaft drives auxiliary units of a valve system, such as a cam shaft, and a water pump.
The front end of the first cylinder head is protruded more forwardly of the internal combustion engine than the front end face of the second cylinder head relative to the axis of the crank shaft. The cylinder heads are provided with first and second rotatable cam shafts. First and second cam shaft sprockets are provided coextensively with one another at the ends of the first and second cam shafts in the front of the V-type internal combustion engine. A timing chain sprocket is provided at the end of the crank shaft in the front of the V-type internal combustion engine, coextensive with the first and second cam shaft sprockets. A timing chain is wound between the timing chain sprocket and the first and second cam shaft sprockets.
In another type of V-type internal combustion engine a timing belt communicates between cam shaft pulleys provided on the cam shafts and a crank shaft pulley on the crank shaft.
Unexamined patent publication No. 67716 of the year 1985 discloses a cooling system for a V-type internal combustion engine which allows less circulating water flow to a cylinder bank in the front than to another cylinder bank in the rear relative to the straight travel direction of the vehicle.
Another type of V-type internal combustion engine is disclosed in unexamined patent publication No. 96737 of the year 1987. In the engine, the water pump and auxiliary components outside the water pump consisting of driven pulleys are accommodated in a V-valley in the upper center of a cylinder block containing two cylinder rows defined by cylinders arranged in series. A timing belt transmission system connecting between the water pump and the crank shaft and a belt transmission system connecting between the auxiliary components and the crank shaft are in as such order successively aligned with a wall opposite to the timing belt in the cylinder block.
In some water pumping apparatuses of conventional internal combustion engines, a water pump is installed directly on the end face of the cylinder block, i.e., the outer side face thereof. Alternatively, it is fitted on a timing chain cover provided with the cylinder block.
The former described above includes those apparatuses in which a water pump pulley is driven by a timing belt, or alternatively, by a V-belt or a V-ribbed belt with the timing belt or a timing chain disposed to avoid a space of installing the water pump.
In the latter described above, the water pump pulley was driven by the V-belt or the V-ribbed belt.
Concomitantly, the internal combustion engine wherein the cam shaft is driven by the timing chain requires driving the water pump pulley using the V-belt or the V-ribbed belt disposed on the outer side of the timing chain. Specifically, the water pump pulley is extended to be driven by the V-belt or the V-ribbed belt independently of a location at which the water pump is disposed. This disadvantageously enlarges the overall length and width of the internal combustion engine, which becomes large in size.
In an attempt to eliminate the problem just mentioned, the present invention is provided for an internal combustion engine wherein a cam shaft is driven by a timing chain. The invention is characterized by: a water pump sprocket disposed coextensively with the timing chain to allow the timing chain to drive the water pump; and the water pump is provided at the end face of the cylinder block within a timing chain cover enclosing the timing chain.
In accordance with the invention as stated above, the water pump is installed at the end face of the cylinder block; the timing chain is wound on the water pump sprocket of the water pump; the water pump and the timing chain are enclosed by a timing chain cover; and the water pump is driven by the timing chain. This reduces the overall length and width of the internal combustion engine.